1. Technical Field of Invention
The invention disclosed and taught herein relates generally to a system and method of use that may be employed to provide artificial gravity in low or zero gravity environments such as outer space, using centrifugal force within a spacecraft.
2. Description of Related Art
Astronauts experience multiple physiological effects in an environment of low or zero gravity such as spaceflight. In situ equipment designs to combat some of these effects have been made and flown in space. The prior art for combating some physiological symptoms during spaceflight includes items such as treadmills or similar exercise devices where an astronaut is bungee-corded to such a device during use. These devices may assist in maintaining muscle strength and mass, cardiac performance, etc., among other potential health benefits. Nevertheless, one negative physiological effect of spaceflight that remains to be successfully addressed is bone mass loss, a process which begins soon after reaching a weightless condition in outer space, which varies both by individual metrics and the duration of weightlessness, and is ameliorated only by individually-varying degrees of recovery upon return to earth where earth-normal gravity (acceleration) is restored. Full recovery of lost bone mass upon returning to earth is not guaranteed, as prior studies on American and Russian astronauts have shown that bone mass loss for some astronauts is still measurable 5 years after completed mission durations ranging from 28-184 days.
Therefore, a need exists for a system and method that may combat the physiological effects of spaceflight in a manner intended to reduce the rate of bone mass loss.
Designs for spacecraft-related, gravity-inducing inventions have been conceptualized in such fictional works as the movie “2001: A Space Odyssey”. While appearing to be fully-conceptualized, the embodied ideas are considered incomplete from an engineering perspective. As an example, early in the movie, the fictional “Pan Am Clipper” spacecraft docks with a fictional earth-orbiting, twin-ring-designed space station that rotates at a constant velocity. In a real-life, ring-design space station, as astronauts and supplies are shuttled between a central docking hub and the “ring floors”, which provide a gravity environment thru centrifugal acceleration, two first-order dynamic effects must be accommodated: 1) in an absence of other controls, the angular momentum of the entire vehicle will be conserved even while there is addition/subtraction of mass at the fixed rotational radius of the “ring floors”. That is, spacecraft rotational speed will increase as astronauts and supplies leave a ring floor, and conversely, rotational speed decreases as astronauts and supplies arrive at a ring floor of such a space station. This conservation of angular momentum produces rotational speed changes as mass locations change, yet this compensatory speed change—the natural physical law “conservation of angular momentum”—is undesirable for maintaining a constant state of acceleration (artificial gravity) at a “ring floor”. As a result, “tip thrusters” or similar attitude control gas jets must be utilized at the periphery of the ring structure in order to maintain constant rpm, being oriented tangentially in either “direction of” or “against” vehicle rotation to speed up or decelerate the spacecraft, respectively, to maintain this desired rpm while the spacecraft's angular momentum changes during crew transfers, etc. The magnitude of required rotational speed adjustment is dependent upon and proportional to the ratio of arriving/departing mass relative to the overall mass at the ring floors, as well as the acceptable rotational speed error for the design. 2) Depending on where astronauts and supplies are already located on the ring floor, adding “new” mass—visitors and supplies—at random positions along a ring floor (or conversely removing them) will change the dynamic balance of the overall vehicle, as will the transition of these masses from any central docking hub to a ring floor. Cross-product torques will also be created should one ring's ring-floor mass change differently from its companion ring. Again, the magnitude of required dynamic balance compensation relates to the percent of mass change. In addition to the previously-identified rpm-control thrusters, some form of dynamic balance compensation is required for proper attitude control, e.g. “out of plane” thrusters clustered around aforementioned speed-control thrusters, or similar means. In both cases, minimizing consumption of reaction control gas is a goal for any real-world, ring-design space station. Other “non-gas-generating” devices for spacecraft attitude control such as momentum wheels used for spacecraft 3-axis stabilization have a scalability problem in structures of this size, as the amount of torque they could produce against the inertia of the overall spacecraft makes them undesirable from both a weight (mass) and efficacy perspective as they generate insufficiently small angular accelerations to compensate for imbalance loads in such conceptually large spacecraft. Meanwhile, if consumables such as reaction control gas are not properly managed, the mission profiles for ring-design spacecraft can become restricted to low earth orbit where resupply missions that “re-stock” a spacecraft's attitude control gas supplies are more easily accomplished. Further, in the same movie, the fictional Discovery One spaceship, a Jupiter-bound spacecraft, incorporates a single gravity-ring centrifuge which allows for running exercise on the ring floor as well as ‘cryo-sleep’ berths for crewmembers in suspended animation, yet no compensating systems for angular momentum changes, reaction torques, or dynamic balance are presented. Similarly, a fan of the Star Trek TV and movie series has identified an idea for a single centrifuge ring to be located within the center disk of the imaginary spaceship USS Enterprise, with no account made for attitude control (reaction torques, dynamic balance, etc.) of that proposed device embodied inside the fictional Enterprise spacecraft.
There is merit in using a centrifuge to simulate a gravity-like environment. For example, ground-based centrifuges are designed to induce radial accelerations that can create many times the acceleration due to gravity via centrifugal force (in a horizontal plane of the centrifuge's rotation) in order to aid in understanding the effects of “high g” (high acceleration) loads on an astronaut's ability to perform necessary mission tasks.
No centrifuge solutions at any fraction or multiple of earth-normal gravity (1-G) for use in space are known at this time, and a need exists for a solution that addresses the unique requirements imposed by applying ground-based radial acceleration design concepts to the inertial (zero-g) environment of outer space.
Moreover, the need exists for a centrifugal rotation system for spacecraft that avoids the problems associated with producing radial accelerations on an entire spacecraft to approximate gravity environments for its occupants, sometimes referred to as “rotisserie mode” in reference to rotating a rigid-body spacecraft (Apollo CSM spacecraft rotated slowly along their centerline axis of symmetry for thermal control on approach to and return from the moon, but not fast enough to generate a significantly-perceived “artificial gravity”). Such “entire spacecraft” centrifugal designs do little to address the fuel consumption problem of constantly adjusting for angular momentum changes as occupants move around or otherwise alter the dynamic balance of the overall rotating system. As habitable interior volumes for envisioned future spacecraft increase, the potential impact to attitude control systems that rely on reaction control gas also becomes apparent. Such an approach has the disadvantage of making a reaction control fuel state (consumables supply) hard to estimate, based on unpredictable crew motions (imbalance load) over extended periods of time, for missions far beyond earth orbit. An additional challenge arises when rotating an entire spacecraft, especially at speeds required for a significant percentage of earth-normal (1-g) gravity: spacecraft-mounted, steerable antennae may be required to “target lock and track” Earth or the nearest communications station in order to maintain constant radio contact as the spacecraft itself rotates. Mission success might now depend on motor component reliability of such a design created to compensate for “whole spacecraft” rotation.
Therefore, a need exists to provide for a spacecraft-internal centrifuge invention for use in a zero-gravity space environment